1. Field of the Invention
The present invention relates to high frequency components having metal covers attached thereto and communication apparatuses including such high frequency components.
2. Description of the Related Art
In a conventional high frequency component, such as a voltage-controlled oscillator (VCO) and a PLL module used in a mobile phone and other communications devices, various kinds of chip components are mounted on a substrate having an electrode pattern provided thereon. In addition, a metal cover is attached to the substrate to cover the top of the substrate including the chip components.
Each of FIGS. 7A and 7B shows such a conventional high frequency component. FIG. 7A shows a perspective view of the high frequency component and FIG. 7B shows a sectional view thereof. In these figures, the reference numeral 1 denotes a ceramic substrate, on which various types of chip components including a chip coil 3 are mounted. A metal cover 2 is fitted over the top of the substrate 1 to cover the top of the substrate 1, on which the chip components are mounted.
In the conventional high frequency component in which the top of the substrate 1 having the chip components mounted thereon is covered with the metal cover 2, the metal cover 2 is in close proximity to the components mounted on the substrate, particularly, in close proximity to the chip coil 3. As a result, the inductance of the chip coil is substantially reduced. In addition, when the attachment position of the metal cover 2 on the substrate 1 changes due to positional inaccuracy in mounting the chip coil 3 on the substrate 1 and dimensional inaccuracy of the metal cover 2, the inductance of the chip coil 3 varies.
As a result, the above-described problems affect the characteristics of high frequency components, such as a VCO and a PLL module. The characteristics thereof deviate from a desired characteristic range, thereby reducing the ratio of non-defective products to defective products.